This article deals with how to do a one-way sync of your appointments on Bookem to your external calendar.
Find out how to sync your Bookem calendar with:
your calendar on your Mac or iOS device
Google or Outlook Calendar
Note: sync isn't immediate; it is completely up to your calendar provider to decide how often to poll Bookem to get the latest bookings.
To do things the other way, i.e. sync your appointments on your external calendar to Bookem, see this article.